Java Backend Engineer (IM Server)

Responsibilities

• Design & implement IM server.
• Develop video/audio conferencing modules.
• Build file management.
• Implement calendar & scheduling: events, invitations, conflict detection, reminders, external integration.
• Solve high-concurrency, low-latency, high-availability challenges.
• Design distributed components: message routing, push, offline messages, data consistency.
• Collaborate with product/client/infra teams on APIs & data models.
• Performance tuning, capacity planning, fault-tolerance for core services.
• Troubleshoot production issues, root cause analysis, monitoring & alerting.
• Code reviews, documentation, knowledge sharing.

Requirements

• Bachelor's degree or above in Computer Science or related fields; 3+ years Java backend.
• Strong Java, concurrency, networking, JVM tuning.
• Familiar with WebSocket/MQTT/SIP/WebRTC signaling is a plus.
• File storage, access control, or calendar logic experience preferred.
• Solid system design; high-traffic, low-latency experience.
• Strong problem-solving, online debugging, performance optimization.
• Good communication, ownership, responsibility.